Multi-layer coil component

ABSTRACT

In the multi-layer coil component, the via conductor electrically connecting the coil layers adjacent to each other in the stacking direction of the element body protrudes from the coil region toward the side surface of the element body when viewed from the stacking direction of the element body. Therefore, the coil has a concave-convex portion. When a force is applied to the multi-layer coil component from the outside, the force is dispersed in the concave-convex portion of the coil, and thus defects are less likely to occur in the coil than in a coil in which the side of the side surfaces is flat.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2021-57711, filed on 30 Mar. 2021, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a multi-layer coil component.

BACKGROUND

Conventionally, known in the art is a multi-layer coil component inwhich a coil having a coil axis parallel to a stacking direction isprovided in an element body having a stacking structure. Japanese PatentLaid-Open No. 1995-317308 (Patent Document 1) discloses a technique offorming a coil layer and a via conductor constituting a coil by using aprinting method.

SUMMARY

In the above-described multi-layer coil component according to theconventional art, when a force is applied from the outside, the forcemay reach the coil to cause a defect in the coil.

As a result of intensive studies, the inventors have newly found atechnique in which a defect is less likely to occur in the coil byincreasing mechanical strength even when a force is applied to amulti-layer coil component from the outside.

According to various aspects of the present disclosure, there isprovided a multi-layer coil component in which mechanical strength of acoil is improved.

A multi-layer coil component according to one aspect of the presentdisclosure including an element body including a plurality of layersstacked and having a pair of end surfaces facing each other in a firstdirection parallel to a stacking direction of the plurality of layersand a side surface connecting the pair of end surfaces, a coil providedin the element body and having a coil axis parallel to the firstdirection; and, a pair of external electrodes respectively provided onthe end surfaces of the element body, wherein the coil having aplurality of coil layers provided between the plurality of layersconstituting the element body and arranged along the first direction;and, a plurality of via conductors provided between the coil layersadjacent to each other in the first direction and electricallyconnecting the adjacent coil layers to each other, wherein, when viewedfrom the first direction, the via conductor protrudes from a coil regionwhere the coil layer is formed toward the side surface of the elementbody.

In the multi-layer coil component, since the via conductor protrudesfrom the coil region toward the side surface of the element body, theconcave-convex portion is formed at the location of the via conductor.When a force is applied to the multi-layer coil component from theoutside, the force is dispersed in the concave-convex portion, hence,defects are less likely to occur in the coil.

In the multi-layer coil component according to another aspect, the viaconductor is formed of a plurality of conductor layers, and has aconcave-convex portion that is concave-convex in a direction orthogonalto the first direction.

In the multi-layer coil component according to another aspect, theconductor layer has a cross-sectional shape in a cross section parallelto the first direction, in which two corners on one end surface side ofthe rectangular element body extending in a direction orthogonal to thefirst direction are rounded.

In the multi-layer coil component according to another aspect, in across section parallel to the first direction, the plurality of viaconductors alternately protrudes from the coil region toward the sidesurface of the element body along the first direction on one side andthe other side in a direction orthogonal to the first direction.

In the multi-layer coil component according to another aspect, in aplurality of cross sections parallel to the first direction, theplurality of via conductors protrudes from the coil region toward theside surface of the element body.

In the multi-layer coil component according to another aspect, theelement body is a sintered element body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the multi-layer coil componentaccording to an embodiment.

FIG. 2 is an exploded perspective view showing a stacked state of theelement body shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along line III-III of the elementbody shown in FIG. 2.

FIGS. 4A to 4D are plan views showing the coil layer constituting thecoil shown in FIG. 3.

FIGS. 5A and 5B are views showing each step in manufacturing the elementbody.

FIGS. 6A and 6B are views showing each step in manufacturing the elementbody.

FIGS. 7A and 7B are views showing each step in manufacturing the elementbody.

FIGS. 8A and 8B are views showing each step in manufacturing the elementbody.

FIGS. 9A and 9B are views showing each step in manufacturing the elementbody.

FIGS. 10A and 10B are views showing each step in manufacturing theelement body.

FIGS. 11A and 11B are views showing each step in manufacturing theelement body.

FIGS. 12A and 12B are views showing each step in manufacturing theelement body.

FIG. 13 is a diagram showing a positional relationship between the coilformation region and the via conductor.

FIG. 14 is a diagram schematically showing a cross-sectional shape ofthe coil.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the accompanying drawings. In the description of thedrawings, the same or equivalent element is denoted by the samereference numeral, and redundant description is omitted.

A structure of a multi-layer coil component according to an embodimentwill be described with reference to FIGS. 1 to 3. As shown in FIG. 1,the multi-layer coil component 10 according to the embodiment includesan element body 12 and a pair of external electrodes 14A and 14B.

The element body 12 has a substantially rectangular parallelepiped outershape and includes a pair of end surfaces 12 a and 12 b facing eachother in the extending direction of the element body 12. The elementbody 12 further includes four side surfaces 12 c to 12 f extending inthe direction in which the end surfaces 12 a and 12 b face each otherand connecting the end surfaces 12 a and 12 b to each other. In thepresent embodiment, the side surface 12 d is a mounting surface facingthe mounting base when the multi-layer coil component 10 is mounted, andthe side surface 12 c facing the side surface 12 d is a top surface whenthe multi-layer coil component 10 is mounted. When the dimension of theelement body 12 in the facing direction of the end surfaces 12 a and 12b is a length, the dimension in the facing direction of the sidesurfaces 12 e and 12 f is a width, and the dimension in the facingdirection of the side surfaces 12 c and 12 d is a thickness, thedimension of the element body 12 is, for example, 1.6 mm length×08 mmwidth×0.8 mm thickness.

The pair of external electrodes 14A and 14B are provided on the endsurfaces 12 a and 12 b of the element body 12, respectively. In thepresent embodiment, the external electrode 14A integrally covers theentire region of the end surface 12 a and the side surfaces 12 c to 12 fof the region adjacent to the end surface 12 a. Similarly, the externalelectrode 14B integrally covers the entire region of the end surface 12b and the side surfaces 12 c to 12 f of the region adjacent to the endsurface 12 b. Each of the external electrodes 14A and 14B includes oneor more electrode layers. For example, a metallic material such as Agmay be used as an electrode material constituting each of the externalelectrodes 14A and 14B.

The element body 12 has a structure in which an internal conductor 18 isprovided inside a magnetic body 16. The element body 12 has a stackingstructure. The magnetic body 16 has a stacking structure in which aplurality of magnetic layers 17 are stacked in a direction in which theend surfaces 12 a and 12 b face each other. In the followingdescription, the facing direction of the end surfaces 12 a and 12 b isalso referred to as a stacking direction or a first direction of theelement body 12.

The magnetic body 16 is made of a magnetic material such as ferrite. Themagnetic body 16 is obtained by stacking and sintering a plurality ofmagnetic pastes (for example, ferrite pastes) to be the magnetic bodylayer 17. That is, the element body 12 has a print stacking structureand is a sintered element body, in which the magnetic layers 17 on whichthe magnetic paste is printed are stacked and sintered. The number ofmagnetic layers 17 constituting the element body 12 is, for example, 120layers. The thickness of each magnetic layer 17 is, for example, 15 μm.In the actual element body 12, the plurality of magnetic layers 17 areintegrated such that boundaries between the layers are not visible.

The inner conductor 18 includes one coil 20 and a pair of leadconductors 19A and 19B. Each of the coil 20 and the lead conductors 19Aand 19B of the inner conductor 18 has a stacking structure in thestacking direction of the element body 12.

As shown in FIG. 3, the coil 20 has a coil axis Z parallel to thestacking direction of the element body 12 and is wound around the coilaxis Z. In the present embodiment, the length of the coil 20 in thestacking direction of the element body 12 is 1.3 mm. In the stackingdirection of the element body 12, the length of the coil 20 can bedesigned to be in a range of 50 to 80% of the length of the element body12. In the present embodiment, the inner diameter of the coil 20 is 0.25to 0.45 mm, for example, 0.3 mm.

In the present embodiment, the coil 20 includes four types of coillayers 21 to 24 as shown in FIGS. 4A to 4D. The coil layers 21 to 24constituting the coil 20 are made of a conductive material containing ametal such as Ag. The coil 20 is formed by a printing method.Specifically, the coil 20 is obtained by applying a conductive paste(for example, Ag paste) to be the coil layers 21 to 24 on a magneticpaste to be the magnetic layer 17 and sintering the conductive paste.The thickness of each of the coil layers 21 to 24 is, for example, 30μm.

Each of the coil layers 21 to 24 has a U-shape when viewed from thestacking direction of the element body 12, and constitutes ¾ turns ofthe coil 20. When viewed from the stacking direction of the element body12, the coil layer 21 has a rotationally symmetric relationship with thecoil layer 22 with respect to the coil axis Z, and when the coil layer22 is rotated 90 degrees clockwise about the coil axis Z, the coil layer22 completely overlaps the coil layer 21. The coil layer 22 is locatedon the upper side of the coil layer 21, and is electrically connected toan end portion 21 b of the coil layer 21 at one end portion 22 a via avia conductor 26 described later.

The coil layer 22 has a rotationally symmetric relationship with thecoil layer 23 with respect to the coil axis Z, and when the coil layer23 is rotated 90 degrees clockwise about the coil axis Z, they aresubstantially aligned. The coil layer 23 is located on the upper side ofthe coil layer 22, and is electrically connected to an end portion 22 bof the coil layer 22 at one end portion 23 a via the via conductor 26described later.

The coil layer 23 has a rotationally symmetric relationship with thecoil layer 24 with respect to the coil axis Z, and when the coil layer24 is rotated 90 degrees clockwise about the coil axis Z, the coil layer24 completely overlaps the coil layer 23. The coil layer 24 is locatedon the upper side of the coil layer 23, and is electrically connected toan end portion 23 b of the coil layer 23 at one end portion 24 a via thevia conductor 26 described later.

The coil layer 24 has a rotationally symmetric relationship with thecoil layer 21 with respect to the coil axis Z, and when the coil layer21 is rotated 90 degrees clockwise about the coil axis Z, the coil layer21 completely overlaps the coil layer 24. The coil layer 21 is locatedon the upper side of the coil layer 24, and is electrically connected toan end portion 24 b of the coil layer 24 at one end portion 21 a via thevia conductor 26 described later.

One set of the coil layers 21 to 24 arranged in order in the stackingdirection of the element body 12 are jointed with end portions thereofoverlapping each other, and constitute three turns of the coil 20surrounding the coil axis Z. In the present embodiment, the coil 20includes a plurality of sets of coil layers 21 to 24.

The coil 20 further includes a plurality of via conductors 26. Theplurality of the via conductors 26 connects the coil layers 21 to 24adjacent to each other in the stacking direction. Each of the viaconductors 26 includes a plurality of stacked conductor layers 25. Inthe present embodiment, the via conductors 26 includes two conductorlayers 25. Similarly to the coil layers 21 to 24, the conductor layer 25constituting the via conductor 26 is made of a conductive materialcontaining a metal such as Ag. Each of the via conductor 26 is formed bya printing method. Specifically, each of the via conductors 26 isobtained by applying a conductive paste (for example, Ag paste) to bethe conductor layer 25 onto the conductive paste to be the coil layers21 to 24 and sintering the conductive paste.

The plurality of via conductors 26 all have the same shape and the samedimensions. As shown in FIGS. 4A to 4D, the via conductor 26 has arounded square shape in which four corners are rounded when viewed fromthe stacking direction of the element body 12. The length of each sideof the via conductor 26 is designed to be larger than the width of eachof the coil layers 21 to 24, and the formation region of the viaconductor 26 is larger than the formation region of the end portion ofthe coil layers 21 to 24. In addition, when the via conductors 26 areoverlapped on the end portions 21 b, 22 b, 23 b, and 24 b of the coillayers 21 to 24, the via conductors 22 are overlapped to protrude in theextending direction of the end portions 21 b, 21 b, 23 b, and 24 b ofthe coil layers 21 to 24.

The conductor layers 25 constituting the via conductors 26 have the sameshape and the same dimensions. As shown in FIG. 3, in a cross sectionparallel to the coil axis Z, the conductor layer 25 has a rectangularcross section extending parallel to the end surfaces 12 a and 12 b ofthe element body 12 and having two rounded corners on the end surface 12a side (so-called semicylindrical cross section). The thickness of eachof the conductor layers 25 is, for example, 30 μm. In the via conductors26, the conductor layers 25 form a concave-convex portion 27 (see FIGS.10A and 10B) that is concave-convex in a direction orthogonal to thestacking direction of the element body 12 (that is, the direction of theside surfaces 12 c to 12 f of the element body 12).

FIGS. 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 10A, 10B, 11A, 11B, 12A,and 12B show a procedure for forming a part of the coil 20 by a printingmethod.

As shown in FIGS. 5A and 5B, first, a conductive paste for forming thecoil layer 22 is printed on the magnetic layer 17 to be a base.

Next, as shown in FIGS. 6A and 6B, a magnetic paste for forming themagnetic layer 17 is printed to completely surround the coil layer 22.As a result, the stack becomes substantially flat.

Then, as shown in FIGS. 7A and 7B, a conductive paste to be the firstlayer of the conductor layers 25 is printed on the end portion 22 b ofthe coil layer 22 exposed on the stack. At this time, since theconductor layer 25 is larger than the end portion 22 b of the coil layer22, the conductor layer 25 protrudes outward from the end portion 22 bof the coil layer 22 as shown in FIG. 7B.

Subsequently, as shown in FIGS. 8A and 8B, a magnetic paste for formingthe magnetic layer 17 is printed to completely surround the first layerof the conductor layers 25. Thereby, the stack is again substantiallyflat.

Next, as shown in FIGS. 9A and 9B, a conductive paste for forming thesecond layer of the conductor layers 25 is printed to overlap the firstlayer of the conductor layers 25. Thus, the via conductors 26 havingtwo-layer structure is formed.

Then, as shown in FIGS. 10A and 10B, a magnetic paste for forming themagnetic layer 17 is printed to completely surround the second conductorlayer 25. Thereby, the stack is again substantially flat.

Subsequently, as shown in FIGS. 11A and 11B, a conductive paste to bethe coil layer 23 is printed. At this time, the end portion 23 a of thecoil layer 23 overlaps the via conductor 26, and the coil layer 22 andthe coil layer 23 are electrically connected via the via conductor 26.

Next, as shown in FIGS. 12A and 12B, a magnetic paste for forming themagnetic layer 17 is printed to completely surround the coil layer 23.Thereby, the stack is again substantially flat.

In FIGS. 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 10A, 10B, 11A, 11B,12A, and 12B, the procedure of providing the coil layer 21 on the coillayer 22 via the via conductor 26 is shown, but the coil layers 21 to 24can be provided by the same procedure as described above.

The multi-layer coil layers 21 to 24 stacked sequentially form arectangular ring coil region C as shown in FIG. 13 when viewed from thestacking direction of the element body 12. The plurality of viaconductors 26 provided to overlap the coil layers 21 to 24 are locatedat any of the four corners of the coil region C. As described above,each of the via conductors 26 is provided to protrude from the endportions 21 b, 22 b, 23 b, and 24 b of the coil layers 21 to 24, andthus protrudes from the inside to the outside of the line Cl definingthe outer shape of the coil region C (i.e., the contour line). As aresult, each of the via conductors 26 protrudes from the coil region Ctoward each of the side surfaces 12 c to 12 f of the element body 12when viewed from the stacking direction of the element body 12. In thiscase, each of the via conductors 26 includes an overlapping part 26 awhich is present in the coil region C (i.e., overlapped on the coillayers 21 to 24) and a non-overlapping part 26 b which is presentbetween the coil region C and the side surfaces 12 c to 12 f of theelement body 12 (i.e., not overlapped on the coil layers 21 to 24), andthe overlapping part 26 a and the non-overlapping part 26 b areintegrated.

Therefore, as shown in FIG. 14, in a cross section parallel to the coilaxis Z, the via conductors 26 protrude further toward the side surfaces12 c to 12 f of the element body 12 than the coil layers 21 to 24.Therefore, as a whole of the coil 20, the concave-convex portion 28 thatis concave-convex in the direction orthogonal to the stacking directionof the element body 12 (that is, a direction toward the side surfaces 12c to 12 f of the element body 12) is formed. The concave-convex portion28 of the coil 20 is concave-convex with respect to all of the four sidesurfaces 12 c to 12 f of the element body 12. The concave-convex portion28 of the coil 20 reaches the lead conductors 19A and 19B. As shown inFIG. 14, in the side surfaces 12 e and 12 f facing each other, thepositions of the concave and the convex of the concave-convex portion 28facing the side surface 12 e and those of the concave-convex portion 28facing the side surface 12 f are shifted from each other. Morespecifically, the plurality of via conductors 26 alternately protrude tothe side surface 12 e side and the side surface 12 f side in the facingdirection of the side surfaces 12 e and 12 f along the stackingdirection of the element body 12, and protrude from the contour line Clof the coil region C.

As described above, the multi-layer coil component 10 includes theplurality of magnetic layers 17 stacked, the element body 12 having thepair of end surfaces 12 a and 12 b facing each other in the firstdirection parallel to the stacking direction of the plurality ofmagnetic layers 17, the coil 20 provided in the element body 12 andhaving the coil axis Z parallel to the first direction, and the pair ofexternal electrodes 14A and 14B provided on the end surfaces 12 a and 12b of the element body 12. The coil 20 includes the plurality of coillayers 21 to 24 provided between the plurality of magnetic layers 17constituting the element body 12 and arranged along the first direction,and the plurality of via conductors 26 provided between the coil layers21 to 24 adjacent to each other in the first direction and electricallyconnecting the adjacent coil layers 21 to 24 to each other. When viewedfrom the first direction, the via conductor 26 protrudes from thecontour line Cl of the coil region C in which the coil layers 21 to 24are formed.

Therefore, as shown in FIG. 14, the coil 20 is provided with theconcave-convex portion 28 from which the via conductors 26 protrude.When a force is applied to the multi-layer coil component 10 from theoutside, for example, from the side of the surfaces 12 c to 12 f, theforce is dispersed in the concave-convex portion 28 of the coil 20, andpropagation of stress is less likely to occur. Therefore, defects areless likely to occur in the coil 12 compared to a coil in which the sideof the side surfaces 12 c to 12 f is flat. That is, in the multi-layercoil component 10, the mechanical strength of the coil 20 is improved.

In addition, in the multi-layer coil component 10, the via conductor 26formed of the plurality of conductor layers 25 has the concave-convexportion 27. Similarly to the concave-convex portion 28 of the coil 20,the concave-convex portion 27 of the via conductor 26 also has afunction of dispersing a force from the outside from the side of theside surfaces 12 c to 12 f. That is, the mechanical strength of the coil20 is further improved by the via conductor 26 having the concave-convexportion 27. In addition, the protruding portions of the concavo-convexportions 27 of the via conductors 26 serve as wedges that engage withthe magnetic layer 17, thereby prevent from shrinkage of the viaconductors 26 (relative shrinkage with respect to the magnetic layer 17)during sintering of the element body 12. Thus, disconnection of the viaconductor 26 can be prevented.

Further, in the multilayer coil component 10, the plurality of viaconductors 26 protrude from the contour line Cl of the coil region C notonly in the cross section parallel to the side surfaces 12 c and 12 d asshown in FIG. 14 but also in the cross section parallel to the sidesurfaces 12 e and 12 f. Therefore, even when an external force isapplied from any side of the side surfaces 12 c to 12 f of the elementbody 12, the force can be dispersed in the concave-convex portion 28 ofthe coil 20.

Although the embodiments of the present disclosure have been describedabove, the present disclosure is not necessarily limited to theabove-described embodiments, and various modifications can be madewithout departing from the gist thereof.

For example, the coil region C may have a polygonal ring shape, acircular ring shape, or an elliptical ring shape. The planar shape ofthe via conductor 26 may be polygonal, circular, or elliptical. Thenumber of conductor layers 25 constituting the via conductors 26 may beone or three or more layers. The cross-sectional shape of the conductorlayer 25 constituting the via conductor 26 may be a semicircular or asemielliptical in which the side of the end surface 12 b is flat.

What is claimed is:
 1. A multi-layer coil component comprising: anelement body including a plurality of layers stacked and having a pairof end surfaces facing each other in a first direction parallel to astacking direction of the plurality of layers and a side surfaceconnecting the pair of end surfaces; a coil provided in the element bodyand having a coil axis parallel to the first direction; and, a pair ofexternal electrodes respectively provided on the end surfaces of theelement body, wherein the coil having: a plurality of coil layersprovided between the plurality of layers constituting the element bodyand arranged along the first direction; and, a plurality of viaconductors provided between the coil layers adjacent to each other inthe first direction and electrically connecting the adjacent coil layersto each other, wherein, when viewed from the first direction, the viaconductor protrudes from a coil region where the coil layer is formedtoward the side surface of the element body.
 2. The multi-layer coilcomponent according to claim 1, wherein the via conductor is formed of aplurality of conductor layers, and has a concave-convex portion that isconcave-convex in a direction orthogonal to the first direction.
 3. Themulti-layer coil component according to claim 2, wherein the conductorlayer has a cross-sectional shape in a cross section parallel to thefirst direction, in which two corners on one end surface side of therectangular element body extending in a direction orthogonal to thefirst direction are rounded.
 4. The multi-layer coil component accordingto claim 1, wherein, in a cross section parallel to the first direction,the plurality of via conductors alternately protrudes from the coilregion toward the side surface of the element body along the firstdirection on one side and the other side in a direction orthogonal tothe first direction.
 5. The multi-layer coil component according toclaim 1, wherein, in a plurality of cross sections parallel to the firstdirection, the plurality of via conductors protrudes from the coilregion toward the side surface of the element body.
 6. The multi-layercoil component according to claim 1, wherein the element body is asintered element body.